DIY Mash Tun Build – Assembly

by Daniel on April 22, 2012

If you have read my post with a shopping list of the parts needed to build a mash/lauter tun (MLT) with a 10 gallon picnic cooler, you’re now ready for the assembly. You need to have two wrenches, at least one 3/4″ wrench, and a second the same size or adjustable in order to tighten these parts together.

Preparation:

removing the stainless braid from the hose

Remove the plastic spigot from your cooler. Use a wrench to hold the plastic nut on the inside and then remove the spigot on the outside. Remove everything except for the inner rubber seal/grommet. If you bought new from Home Depot, you’ll have a white rubber grommet. The used one I bought had no seal, so I purchased a grommet from ACE Hardware for cheap (see previous post).

Optional: Make a mix of hydrogen peroxide & vinegar 1:2 ratio and soak all the brass parts in it (see prev post) in order to remove trace amounts of lead and such. 5 minutes is all you need.

Wrap all threaded ends of your parts with a few wraps teflon tape – do this in a clockwise fashion so that when screwing a part on, it is with the grain of the tape.

If you haven’t already, use a hacksaw to cut the ends of your stainless steel supply hose off (I had the guys at Home Depot do this for me). Grab one end of the stainless steel braid with needle nose pliers and PUSH toward the other end of the hose, it should begin to slide off quite easily. If you pull, it’s like a Chinese finger trap and you’ll just ruin the braid.

Assembly:

Apply some keg lube (food grade petroleum jelly) to the grommet and then pass the brass nipple through the hole. The lube makes it easy for the nipple to fit through. Oh yes, I said it.

grommet and brass nipple

On the inside, slide the stainless steel washer over the nipple.

Screw the female-female coupler onto the nipple also on the inside (see photo below) – you can’t tighten this fully until you’ve attached the ball valve on the outside (step 5)

Externally, add the 3 fender washers to act as spacers which will allow a tight fit of the ball valve.

adding fender washers and ball valve

Attach the ball valve, followed by the male barb connecter.

ball valve & male barb

Tighten the outside and inside parts simultaneously with your wrenches until very snug.

Continue internal assembly: attach brass “tee” to the coupler, tightening so that the arms of the tee are horizontal.

tee attached to coupler

Attach female barb connectors to each end of the tee.

barbs attached

Make a circle with the stainless steel braid with one end on each female barb connector. Tie down with zip-ties. (Stainless steel hose clamps often still corrode because the screw part is not stainless).

completed false bottom assembly

Test! Make sure the ball valve is closed, add water and let sit to check for leaking. Then open to make sure it drains properly.

Hey there,
Thanks so much for the clear and simple instructions. Put this together and made my first-ever all-grain batch without a hitch!
I have a question about the SS braid – when you first put the MLT together, it sits nicely at the bottom of the cooler, circling around the circumference of the bottom, but after mashing and cleaning, it’s kind of twisted and no longer holding its shape. Is there a way to remedy this, or is it even a problem? Any advice is appreciated. Thanks!

Hi Kevin, glad to hear it was a success! The twisting of the braid is one of the reasons I ended up switching to a SS false bottom (but it lets more gunk through than the braid). I just try to really be careful when stirring up my mash as I’m mashing in that I’m not stabbing or hitting the braid at all when I’m stirring with my SS spoon. Staying just above the bottom of the tun as stirring seems to do the trick – but it may need replacement after a while. Overall even if it looks mangy, as long as it drains/sparges without clogging, it should be fine – just want to be sure it’s spread fairly evenly in the grain bed and not crumpled in one place. Good luck!

Just wrapped up making this, and a few thoughts. This was a very easy to follow instructional, so thank you. My igloo was much more than you suggested so my project ended up around $150. I didn’t read closely enough and cleaned all of my parts including the washers in the peroxide/vinegar solution – that was a mistake as it tarnished the washers. Probably no harm. Even adding a 4th washer I still don’t feel the mechanism is tight enough but its not leaking so ploughing ahead. My hardware store sold me flared female 3/8 barb connectors. He swore they were okay to use, we’ll find out. Cutting the hose was the most difficult part for me. It really ripped up the ss hose covering. I ended up trimming with a scissors for a cleaner finish and it was fine but I’m not sure how you just cut through with a hacksaw…where specifically are you supposed to cut – on the hose on the metal end cap or somewhere else?

One more thing. I tried to use the grommet that came with the cooler and it just got ripped to shreds in the process. When I bought the one you suggested it worked perfectly. So spend the extra pennies.

Daniel: I have a 10 gal Home Depot/Rubbermaid cooler. Did you do anything to seal between the stainless steel washer and the brass coupling inside the MLT? I feel like this could be a place that might allow water to get through as it’s not a gasketed seal. Am I overthinking this?

Thanks for the instructions! I spent all day gathering parts and returning to the store for different parts and what not. Easily found a commercial hardware store that had the stainless steel washers in 5/8″….bag of 25 was the smallest order I could get!

Also, the Watts A-168 Flare to Flare to Flare Tee 3/8″ was not at Home Depot or Lowes, nor True Value. I ended up going to a local plumbing store and getting a female version of the tee and going with all male hose barb adapters. No biggie, just frustrating looking for that one piece.

Anyway, here’s my question. Tightening everything down, I have a good amount of exposed threads with the teflon tape showing. Not a problem on the outside, but will that be a problem inside the MLT? I’m not sure if it’s OK to have the wort touching that or not.

Hi Derek, I’m sorry you had so much trouble finding that one part. As for your question, it should not be a problem inside the MLT for your mash, I had a little left showing and have had many a brew go just fine. Happy brewing!

Just finished making this and your guide was super helpful! Thanks for posting all the specific item numbers, that helped a lot. I went to Home Depot and had to click the link you had for the gasket to be able to find it. I was actually able to find the right size stainless washer at Home Depot, but it was in a kit for a large bolt with a bunch of other stuff I didn’t need, worth it not to drive around town though. I also used an Igloo brand cooler (orange and white), and the original valve and hole in it were for a 1/2″ valve. With the washers and gaskets it sealed up great with the 3/8″ pieces though. Thanks again!

Hi, thanks for the instruct able. I got this built and just made my first all-grain batch. I used the 10-gal beverage cooler (blue Igloo).

One thing I ran into was my mash lost 7 degrees over 90 minutes. I did a little research and it turns out some of the beverage coolers have hollow lids, no insulation to them. I could literally put my hand on the lid and feel the heat radiating out.

The fix most people are employing is to drill 2-3 holes in the top of the lid and then use the spray foam to fill the hollow cavity with the expanding foam. By drilling the holes on the outside of the lid it prevents the foam from being exposed to the moisture inside the tun and possibly leaching anything into the mash.

I think I am also going to apply the spray foam on the inside cavity portion of the lid but seal it with an epoxy resin that will make it water-proof and then the moisture shouldn’t be an issue anymore.

thanks. I built this today. I was really wavering between the 5G cooler and the 10G… everyone always says “go bigger, you will not regret it,” but I brew mostly 2.5G batches, and the 10G cooler is a pain in the butt in terms of not fitting under my faucet, cleaning etc… I went with it anyway…

I must be a plumbing idiot, because I had major trouble getting the ball valve and the coupling to thread onto the nipple. each only threaded down like 1/4 inch or less, compared to the female barb connecters which easily threaded all the way onto the tee…. I dunno what I did wrong, but I just added extra washers and I don’t think it’s leaking…

ps – the first Ace hardware I went to had 5/8 stainless steel washers, so that was lucky…

Glad to hear the build went okay. I’m wondering if you just got a brass nipple that was just slightly off when made, or the ball valve. It should go on further than that. Weird. I’m glad to hear there’s no leaks and that you found SS washers though, nice!

Great ideas; I read Palmer’s book and another about building a MLT, and now after reading your posts, I’m going to try it this weekend. One question, how do you clean the braid? Are you removing it from the brass fittings?

Thanks Paul! At the end of brew day, I first rinse the majority of the grain out with water. Then I just put some hot water & oxy clean in, rinse it around again, and then drain through the spigot. The braid cleans out very well with this method still after many brews!

No leaks! Home Depot 10 gallon. Took me a few hours start to finish – had to redo the whole valve connection a few times. But it worked great on the first test with water. Ready for brew day! Great approach to building a mach tun. THANKS!

Hi Bill, great question. I found the braid can get a little pinched in places over time, mainly due to stirring up the mash with my big stainless steel spoon, but it still held up this whole time and never had problems sparging. When I built one for my friend, I added some bendable stainless steel wire that I coiled around the whole thing to protect it from this issue. But like I said, even when it gets some wear and tear, it still holds up fine.

Hello Daniel,
I was thinking of using copper tubing inside the braid. I would use a dremel to cut slots horizontally in various places to allow flow from anywhere along the tube. This might be unnecessary.

Thanks for the instructions! This cooler turned out really well with some simple mods. I used the Home Depot 10 Gallon Rubbermaid. I had to add an extra two washers on the outside and one extra on the inside. I also had to flip the ball valve upside down, because the plastic around the inlet hits the valve when right side up, not allowing a full close.

Other than that, I am super excited to try this out on the May4th National Brew Day as my first leap into AG brewing! Thanks again for the instructions.

First AG in the primary today. The mash/lauter tun you advised building here worked great! I will be sure to share your page with others. Also, thanks for the step-by-step first AG brew instructions. I used those today and subbed my own steps for the Pointer’s Proper for AHA Brew Day today. Thanks again!

Thanks Michael, I’m honored that you’re so pleased with my instructions and I’m glad they worked so well for you. I cant wait to hear how the beer tastes! I’m curious: Did you have to modify the various water amounts much for your batch? Did you measure/hit your OG & FG?

Yes. I was using about 8 lbs of grain in my batch. Therefore, I increased to an overall water usage of about 7.5 gal. Using about 2.75 for mash and 4.75 for sparge. I initially was worried about collecting more than the recommended 6.25 gal of wort, but noticed only about 1 gal left in the m/l tun. I collected just over 7 gal of wort and was able to hit the accurate OG/FG.

Daniel, great post. REALLY clarified some stuff for me. My big question is: will this work for the 5 gallon coolers, too? The spigot hole is large enough for a 1/2″ nipple to fit through with no wiggle. If I do the grommet and 3/8″ nipple, is that going to create good seal?

I’ve already built a CPVC manifold, I’m just trying to figure out how to put all of this together without having to buy too many other parts.

Hi Giles,
I’m glad to hear that my post helped you! Yes, I believe this all works for the 5 gallon coolers as well. I definitely recommend the grommet & 3/8″ nipple as this will secure a good seal for you so you don’t get any leaks. I’d love to see pictures of your final product with the CPVC manifold if you’re willing to email me when you’re done, as I could share it on the post as another option for the build. Let me know how it turns out!

Hey Daniel, just wanted to let you know that the recipe turned out absolutely wonderful! By far the best batch I’ve ever brewed. I am one that likes to allow plenty of time for conditioning and carbonation so I’ve only sampled one bottle just yesterday of my first batch that I brewed in October.
I also used the loop tubing in the mash tun and I’ve brewed 5 different recipes so far and have not had one even close to being stuck.
Thanks again

Hi Jamie, thank you, and good question. I have fly sparged with this setup successfully. The loop provides much better surface area and even distribution of water flow through the grain. Just make sure to keep your flow rate slow – sparging should take at least 40 minutes if you really want to extract as much sugar as possible from the grain. It’s worth the extra time. Good luck!

Hey, thanks for posting this! I followed your directions and made a mash tun and I also used your recipe and step by step instructions to make my first all grain batch. I decided to switch to all grain after years of being disappointed with my extract brews that nearly all had the infamous “twang”.

Everything went real smooth but I have one question. During the boil (before starting the hop additions) I started to get what I can only describe as egg drop soup effect. Skim particles floating about for nearly the entire boil. They seemed to filter out after I strained the cooled wort. Did you experience this with your boil?

Hi Paul, thanks for the comment. I’m glad to hear you finally took the leap–you won’t regret it! You have an excellent question. What you are experiencing as the “egg drop soup effect” is what is called the hot break. As the wort begins to boil, proteins in the wort start to coagulate (clump up). At first the coagulation forms foam (why you have to watch for boil overs at this critical time). However, once the “hot break” point is reached, these coagulated proteins have reached large enough size that they fall back down into the wort. This gives the wort the “egg drop soup” appearance as you describe.

The reason you may not have experienced this before when doing extract only brewing is that in the process of the companies producing the extracts, they perform a boil and reach the hot break, so that has already occurred before you even start your boil, thus it’s often not seen. The hot break which forms this egg drop soup is actually a good thing that you want to see. The hot break proteins that coagulate and fall out of your wort can contribute to haze and flavor issues down the road. So when you cool your wort and transfer to your primary, just make sure you leave all the particles that have settled to the bottom and you’re good to go!